Technically they are the ROBUST Equipments.We are FLEXIBLE Systems ( DX200&AXE10).Most of the times we have to do some alteration in our Systems. :-))
But nowadays EWSD D900 is Quiet Great Switch.Which is used by BSNL for GSM Networks.
Techically all switches are at same level.But it depends upon the Party who handles the switch.
Have you ever seen a CDOT with C7 ?